Cytotoxicity of nanostructured vanadium oxide on human cells in vitro.

Vanadium oxide nanostructures have potential uses for electrochemistry and catalysis, yet little is known about their toxicology. In this study, cultured human colon carcinoma cells (Caco-2) were exposed to vanadium oxide and their viability assessed with the neutral red assay. Cells exposed to either vanadium oxide (powdered form) or ethylene diamine intercalated vanadium oxide (enH(2))V(7)O(16) demonstrated no significant reduction in viability after twenty-four hours, yet cells exposed to vanadium oxide nanotubes demonstrated a significant loss in viability after four hours. The physical size and structure of the nanotubes may play an important role in their cytotoxic effects, and the safety of using such nanomaterials must be considered.

Ingestion and inactivation of bacteriophages by Tetrahymena.

Abiotic factors are thought to be primarily responsible for the loss of bacteriophages from the environment, but ingestion of phages by heterotrophs may also play a role in their elimination. Tetrahymena thermophila has been shown to ingest and inactivate bacteriophage T4 in co-incubation experiments. In this study, other Tetrahymena species were co-incubated with T4 with similar results. In addition, T. thermophila was shown to inactivate phages T5 and lambda in co-incubations. Several approaches, including direct visualization by electron microscopy, demonstrated that ingestion is required for T4 inactivation. Mucocysts were shown to have no role in the ingestion of T4. When (35)S-labeled T4 were fed to T. thermophila in a pulse-chase experiment, the degradation of two putative capsid proteins, gp23(*) and hoc, was observed. In addition, a polypeptide with the apparent molecular mass of 52 kDa was synthesized. This suggests that Tetrahymena can use phages as a minor nutrient source in the absence of bacteria.